1. Field of the Invention
The present invention relates in general to passenger detection systems and methods, and relates in particular to an improved passenger detection system that places the airbag for the passenger, in the deployable or not-deployable state, depending on the seating conditions of the passenger sitting in the passenger seat in an automobile.
This application is based on Japanese Patent Applications Nos. Hei 10-061299, Hei 10-077870, Hei 10-077871, Hei 10-077872, Hei 10-077873, Hei 10-083797, Hei 10-083798, Hei 10-083799, Hei 10-097782, and Hei 10-153270, the contents of which are incorporated herein by reference.
2. Description of the Related Art
In general, an airbag apparatus in an automobile is aimed at protecting the driver of the vehicle from fatal injuries, in the event of a collision, and is now considered to be an essential item for automotive safety, and in recent years, an airbag is provided for the passenger as well as for the driver.
An example of such an airbag apparatus is shown in FIG. 96, and is comprised by: a driver-side squib circuit comprised by a series circuit including safety sensor SS1, squib SQ1, and a semiconductor switching device SW1 such as field effect transistor; a passenger-side squib circuit comprised by a series circuit including a safety sensor SS2, a squib SQ2, and a semiconductor switching device SW2 such as field effect transistor; an electronic accelerometer (impact sensor) GS; a control circuit CC for judging an impact force on the basis of output signals from the sensor GS, and to supply signals to the gate circuits of the switching devices SW1, SW2.
This air bag apparatus, when a collision occurs for whatever reason, safety sensor SS1, SS2 are closed responding to a relatively minor acceleration, and the squib circuits are placed in an operable state. And, when the control circuit CC judges that a collision has definitely taken place according to the signals from the accelerometer GS, signals are sent to the gates of switches SW1, SW2 and the switches SW1, SW2 are closed. As a result of a current flowing in the respective squib circuits, the driver-side and passenger-side airbags are deployed because of the heating in the squib SQ1, SQ2, and the occupants are protected from the collision impact.
However, this type of airbag apparatus is designed so that the airbags are deployed upon collision, regardless of the presence of a passenger so that, when an adult is sitting on the passenger seat, protective effect against collision can be expected, but when a child is sitting on the passenger seat, because the seated height is shorter and the head position is lower than an adult, the effect of airbag deployment on the child can be more damaging. Therefore, in some cases, it may be desirable that the airbag on the passenger-side be not deployed upon collision, when the passenger is a child.
Accordingly, in the past, an airbag apparatus such as the one shown in FIG. 97 has been proposed to address such a concern. This airbag apparatus includes a sensor SD to detect whether a passenger is seated, and the control circuit CC judges the seating condition according to the detected signal from the sensor SD, when a collision occurs, it is designed so that the control circuit CC makes the airbag apparatus deployable or not deployable. Proposed systems are based on: either to measure the weight of the passenger according to a weight sensor to decide if the passenger is an adult or a child; or to record an image of the passenger and decide between an adult or a child based on the processed image.
The weight method is capable of estimating substantially whether the passenger is an adult or a child, and based on the result, the airbag is placed either in the deployable state or not-deployable state, to safeguard the passenger in the event of a collision. However, body weight is subject to individual differences, and there is a serious concern in basing such a critical decision solely on loading factor, and the efficacy of such a system is in doubt.
The imaging method is able to reasonably estimate the seating condition of the passenger and decide whether the passenger is an adult or a child, but the method is based on comparing the current image data with various stored patterns so that the apparatus can be complex and expensive.